1. Field of the Invention
The invention relates to a connection-oriented network node. For example, the invention relates to a technology for rerouting a failure point while assuring a bandwidth when a failure occurs in a connection-oriented network such as a label forwarding network (MPLS (Multi-Protocol Label Switching)) for forwarding data in a way that attaches a label to a packet.
2. Description of the Related Art
A conventional method is exemplified such as Fast Rerouting (Internet Draft: draft-ietf-mpls-rsvp-lsp-fastreroute-07.txt) that is being examined by IETF (Internet Engineering Task Force). In this technology, a protection path rerouting the failure point is previously set up on the assumption of node/link failures. If the failure occurs, a failure detecting node promptly switches over the traffic on a working path passing the failure point to the protection path for rerouting the failure point. With this contrivance, the traffic can be restored from the failure at a high speed.
As to the link failure, however, it is requested that the protection path is set up for on a link-by-link basis (per link). Therefore, if a network is scaled up, the number of the protection paths rises. Herein, if communication qualities (Quality of Service (QoS)) are considered about the network, it is required preparation of enormous spare resources.
In this respect, SRLG (Shared Risk Link Group) is exemplified as a method of sharing the standby resources. This method is that network resources (i.e., nodes and links) having a possibility of suffering simultaneous occurrence of failures are distinguished, and the protection paths different in terms of the SRLG of the network resources to be protected shall share the bandwidths. This scheme enables the standby resources to be reduced.
Non-Patent document 1 describes a brief concept of the SRLG. This document discloses the following. Even when employing two different logical links in a certain network and when these links employ the same physical line, if a failure occurs in the physical line, both of the logical links suffer the failure. Therefore, it is recognized by the SRLG whether the simultaneous failure might occur or not.
Further, “Bandwidth Management Method for Supporting Standby Bandwidth Shared Protection in Mesh Network” disclosed in Patent document 1 is given as a method that actualizes sharing the bandwidths by assigning (applying) the SRLG.    [Patent document 1] Japanese Patent Application Laid-Open Publication No. 2003-115872    [Patent document 2] Japanese Patent Application Laid-Open Publication No. 2004-40384    [Non-Patent document 1] “INTER-AREA ROUTING, PATH SELECTION AND TRAFFIC ENGINEERING”, Version 1, Ben Wright, Internet, November, 2003, http://www.dataconnection.com/network/download/whitepapers/interarea.pdf”
The prior art using the SRLG described above includes a problem that the operation becomes complicated. Namely, in the prior art, for actualizing the bandwidth sharing, even in a case where it is recognized that each of the logical links on the network is explicitly configured by a different physical link, an identifier named SRLG must be assigned to all the network resources in order to actualize the bandwidth sharing.
Further, execution of the failure restoration involves performing setup of the working path, setup of the protection path for bypassing the failure point and setup of the working path to be protected by the protection path.
Moreover, in the case of adopting a method of bypassing the failure in every segment consisting of a plurality of consecutive nodes and links, such a scheme is required that an error in a protection section (segment) is detected by an originating (head-end) node (i.e., a switching node for switching over (bypassing) the working path to the protection path when the failure occurs, and there might be a case of representing this switching node also as “PLR: Point of Local Repair”) of the protection path. For instance, it is considered to adopt such a method of setting up a monitoring path in the segment and, as triggered by a failure in the monitoring path, notifying the PLR of this failure.
For actualizing this scheme, however, the working path, the protection path and the monitoring path are set up respectively and are required to be associated with each other. At this time, further, a requirement is to pay attention so that the monitoring path is coincident with the segment.
As a matter of fact, in the case of configuring a network robust against a physical failure, it is sufficiently considered to select a different physical link at a designing stage so as not to stop the communications with a plurality of local areas due to one failure point.